This invention relates to reinforced hose and more particularly to an improved method for manufacturing a reinforced hose of a type having a reinforcement braiding extending over and bonded to a rubber core and, optionally, having an outer coating bonded to the braiding.
It is common to manufacture hose from a vulcanizable elastomeric material, such as a natural or synthetic rubber. However, a hose formed simply from vulcanized rubber has limited strength and, when the hose is bent, there is a tendancy for the hose to flatten or collapse at the point of bend. In order to eliminate these difficulties, it is common to braid or wind a reinforcement about the rubber core tube. To be effective, the reinforcement must be bonded to the core tube. Normally to obtain a good bond between the reinforcement and the core tube, it has been necessary to apply the braid to the core tube prior to curing the rubber forming the core tube. In addition, it has been common to treat the reinforcement with an adhesive. An outer cover may be applied to the reinforced tube, either by coating or by extrusion and the tube then is cured to form the final hose. Extreme care must be taken during the application of the reinforcement to the uncured core tube to prevent deformation of the tube. If the reinforcement is braided directly onto the uncured tube, there may be a tendancy for the reinforcement to compress and reduce the diameter of the tube. This problem may be eliminated by braiding onto a tubular mandrel through which the core tube is passed and sliding the braiding from the mandrel onto the tube. However, this is a slow process. Care also must be taken to prevent distortion of the uncured hose during the final curing process. One method commonly used for preventing distortion of the hose during the final curing is the lead-press method which involves forming a lead sleeve about the uncured hose, curing the hose and finally removing the lead sleeve. This process also is slow and adds considerably to the cost of manufacturing the hose.
Another method for forming a reinforced hose which is disclosed in U.S. Pat. Nos. 4,104,098 and 4,200,125, involves extruding a core from vulcanizable rubber. The uncured core is passed through a microwave oven and, at the same time, the outer surface of the core contacted with cool fluid so that the core becomes substantially cured at its center and has an uncured outer surface. The cured center region of the core provides sufficient rigidity for applying the reinforcement. A liquid adhesive then is applied to the reinforced tube, any outer coating required is applied and the tube is cured. Again, the partially cured core provides sufficient rigidity to prevent distortion during the final curing. The initial formation of the core must be carefully controlled to prevent either 100% curing of the core, in which case insufficient bonding will take place between the core and the reinforcement, and to prevent insufficient curing of the core, in which case the core may become distorted during the subsequent application of the reinforcement and the final curing steps.